“…Anaerobic digestion is a well-known valorization method for complex waste materials and, for example, across Europe there are over 17,000 biogas plants (situation in the end of the year 2016; EBA, 2018). VFAs, for example, acetic acid, butyric acid, or lactic acid, are produced industrially with certain bacterial strains or pure cultures (Cavinato, Frison, et al, 2017), and the substrates suitable for these processes are usually simple molecules, for example, C5 and C6 sugars (Baumann & Westermann, 2016). The production of VFAs through mixed consortia fermentation can utilize more complex substrates in nonsterile conditions (Jankowska, Chwiałkowska, Stodolny, & Oleskowicz-Popiel, 2015;Jankowska, Duber, Chwialkowska, Stodolny, & Oleskowicz-Popiel, 2018).…”